Hydrothermal silicification and hypogene dissolution of an exhumed Neoproterozoic carbonate sequence in Brazil: Insights from fluid inclusion microthermometry and silicon-oxygen isotopes

Luca Pisani; Gabriella Koltai; Yuri Dublyansky; Barbara I. Kleine; Martin J. Whitehouse; Etienne Skrzypek; Cristina Carbone; Christoph Spötl; Marco Antonellini; Francisco H. Bezerra; Jo De Waele

doi:10.1111/bre.12748

Hydrothermal silicification and hypogene dissolution of an exhumed Neoproterozoic carbonate sequence in Brazil: Insights from fluid inclusion microthermometry and silicon-oxygen isotopes

Luca Pisani^*, Gabriella Koltai, Yuri Dublyansky, Barbara I. Kleine, Martin J. Whitehouse, Etienne Skrzypek, Cristina Carbone, Christoph Spötl, Marco Antonellini, Francisco H. Bezerra, Jo De Waele

^*Corresponding author for this work

Science Institute

Research output: Contribution to journal › Article › peer-review

Abstract

Hypogene dissolution-precipitation processes strongly affect the petrophysical properties of carbonate rocks and fluid migration pathways in sedimentary basins. In many deep carbonate reservoirs, hypogene cavernous voids are often associated with silicified horizons. The diagenesis of silica in carbonate sequences is still a poorly-investigated research topic. Studies exploring the complexity of silica dissolution-precipitation patterns in hypogene cave analogues are therefore fundamental to unravel the diagenetic and speleogenetic processes that may affect this kind of reservoir. In this work, we investigated an exhumed and silicified Neoproterozoic carbonate sequence in Brazil hosting a 1.4 km-long cave. Quartz mineralization and silicified textures were analyzed with a multidisciplinary approach combining petrography, fluid inclusion microthermometry, silicon-oxygen stable isotope analyses and U-Th-Pb dating of monazite crystals. We found that an early silicification event caused the replacement of the dolostone layers with micro-crystalline quartz forming chert nodules. This event was likely associated with mixing fluids (ancient Neoproterozoic seawater and hydrothermal solutions sourced from the underlying Mesoproterozoic basement) at relatively low temperatures (ca. 50–100°C) and shallow depth. After the tectonic deformation produced by the Brasiliano orogeny, silica dissolution was promoted by high temperature and alkaline hydrothermal solutions rising from the quartzite basement along deep-rooted structures. Hypogene hydrothermal alteration promoted the dissolution of the cherty layers and the precipitation of chalcedony and megaquartz. Homogenization temperatures from primary fluid inclusions in megaquartz cement indicate minimum formation temperatures of 165–210°C. Similar temperature estimates (110–200°C) were obtained from the δ³⁰Si and δ¹⁸O isotope systematics of quartz precipitated from hydrothermal solutions. The dissolved salts in the fluid inclusions were evaluated as NaCl + CaCl₂ from microthermometric data combined with cryogenic Raman spectroscopy, corresponding to salinity ranging between 17 and 25 wt.%. No reliable age constraints for hydrothermal silica dissolution-precipitation phases were obtained from monazite U-Th-Pb dating. However, our results, interpreted in the regional context of the São Francisco Craton, suggest that the Cambrian tectono-thermal events could have been amongst the possible drivers for this hypogene process in the basin.

Original language	English
Journal	Basin Research
DOIs	https://doi.org/10.1111/bre.12748
Publication status	Accepted/In press - 2022

Bibliographical note

Funding Information:
This research was carried out in association with the ongoing R&D project registered as ANP 20502‐1, ‘—)—Porokarst—Processes and Properties in Fractured and Karstified Carbonate Reservoirs, sponsored by Shell Brasil under the ANP R&D levy as ‘’. Cave map data were kindly provided by (GPME). Cave sampling was performed through SISBIO permit 63178/1. We sincerely thank the Iramaia municipality (State of Bahia) and the Brazilian Federal Environmental Agency () for providing access to the cave and the special permission for collecting rock samples. We thank Bastian Joachim‐Mrosko for providing the access to the Raman Spectroscopy Laboratory at the University of Innsbruck and for his valuable help. We also thank Jürgen Konzett for the early discussions on monazite dating and Augusto Auler for the help during fieldwork. We finally thank the Editor Atle Rotevatn for handling the manuscript and the reviewers Marjan Temovski, Cathy Hollis and Alexander Klimchouk for their suggestions and comments that helped to improve our paper. This article is the NordSIMS published contribution n. 726. Processos e Propriedades em Reservartorios Carbonaticos Fraturados e Carstificados POROCARSTE 3D’ (UFRN/UNB/UFRJ/UFC/Shell Brasil/ANP Compromisso de Investimento com Pesquisa e Desenvolvimento Grupo Pierre Marin de Espeleologia Instituto Chico Mendes

Publisher Copyright:
© 2022 International Association of Sedimentologists and European Association of Geoscientists and Engineers and John Wiley & Sons Ltd.

Other keywords

fluid flow
hydrothermal karst
silica dissolution
silicified reservoirs

Access to Document

10.1111/bre.12748

Cite this

Pisani, L., Koltai, G., Dublyansky, Y., Kleine, B. I., Whitehouse, M. J., Skrzypek, E., Carbone, C., Spötl, C., Antonellini, M., Bezerra, F. H., & De Waele, J. (Accepted/In press). Hydrothermal silicification and hypogene dissolution of an exhumed Neoproterozoic carbonate sequence in Brazil: Insights from fluid inclusion microthermometry and silicon-oxygen isotopes. Basin Research. https://doi.org/10.1111/bre.12748

@article{8088614545624fbea8a17dc39d43f0b8,

title = "Hydrothermal silicification and hypogene dissolution of an exhumed Neoproterozoic carbonate sequence in Brazil: Insights from fluid inclusion microthermometry and silicon-oxygen isotopes",

abstract = "Hypogene dissolution-precipitation processes strongly affect the petrophysical properties of carbonate rocks and fluid migration pathways in sedimentary basins. In many deep carbonate reservoirs, hypogene cavernous voids are often associated with silicified horizons. The diagenesis of silica in carbonate sequences is still a poorly-investigated research topic. Studies exploring the complexity of silica dissolution-precipitation patterns in hypogene cave analogues are therefore fundamental to unravel the diagenetic and speleogenetic processes that may affect this kind of reservoir. In this work, we investigated an exhumed and silicified Neoproterozoic carbonate sequence in Brazil hosting a 1.4 km-long cave. Quartz mineralization and silicified textures were analyzed with a multidisciplinary approach combining petrography, fluid inclusion microthermometry, silicon-oxygen stable isotope analyses and U-Th-Pb dating of monazite crystals. We found that an early silicification event caused the replacement of the dolostone layers with micro-crystalline quartz forming chert nodules. This event was likely associated with mixing fluids (ancient Neoproterozoic seawater and hydrothermal solutions sourced from the underlying Mesoproterozoic basement) at relatively low temperatures (ca. 50–100°C) and shallow depth. After the tectonic deformation produced by the Brasiliano orogeny, silica dissolution was promoted by high temperature and alkaline hydrothermal solutions rising from the quartzite basement along deep-rooted structures. Hypogene hydrothermal alteration promoted the dissolution of the cherty layers and the precipitation of chalcedony and megaquartz. Homogenization temperatures from primary fluid inclusions in megaquartz cement indicate minimum formation temperatures of 165–210°C. Similar temperature estimates (110–200°C) were obtained from the δ30Si and δ18O isotope systematics of quartz precipitated from hydrothermal solutions. The dissolved salts in the fluid inclusions were evaluated as NaCl + CaCl2 from microthermometric data combined with cryogenic Raman spectroscopy, corresponding to salinity ranging between 17 and 25 wt.%. No reliable age constraints for hydrothermal silica dissolution-precipitation phases were obtained from monazite U-Th-Pb dating. However, our results, interpreted in the regional context of the S{\~a}o Francisco Craton, suggest that the Cambrian tectono-thermal events could have been amongst the possible drivers for this hypogene process in the basin.",

keywords = "fluid flow, hydrothermal karst, silica dissolution, silicified reservoirs",

author = "Luca Pisani and Gabriella Koltai and Yuri Dublyansky and Kleine, {Barbara I.} and Whitehouse, {Martin J.} and Etienne Skrzypek and Cristina Carbone and Christoph Sp{\"o}tl and Marco Antonellini and Bezerra, {Francisco H.} and Jo De Waele",

note = "Funding Information: This research was carried out in association with the ongoing R&D project registered as ANP 20502‐1, {\textquoteleft}—)—Porokarst—Processes and Properties in Fractured and Karstified Carbonate Reservoirs, sponsored by Shell Brasil under the ANP R&D levy as {\textquoteleft}{\textquoteright}. Cave map data were kindly provided by (GPME). Cave sampling was performed through SISBIO permit 63178/1. We sincerely thank the Iramaia municipality (State of Bahia) and the Brazilian Federal Environmental Agency () for providing access to the cave and the special permission for collecting rock samples. We thank Bastian Joachim‐Mrosko for providing the access to the Raman Spectroscopy Laboratory at the University of Innsbruck and for his valuable help. We also thank J{\"u}rgen Konzett for the early discussions on monazite dating and Augusto Auler for the help during fieldwork. We finally thank the Editor Atle Rotevatn for handling the manuscript and the reviewers Marjan Temovski, Cathy Hollis and Alexander Klimchouk for their suggestions and comments that helped to improve our paper. This article is the NordSIMS published contribution n. 726. Processos e Propriedades em Reservartorios Carbonaticos Fraturados e Carstificados POROCARSTE 3D{\textquoteright} (UFRN/UNB/UFRJ/UFC/Shell Brasil/ANP Compromisso de Investimento com Pesquisa e Desenvolvimento Grupo Pierre Marin de Espeleologia Instituto Chico Mendes Publisher Copyright: {\textcopyright} 2022 International Association of Sedimentologists and European Association of Geoscientists and Engineers and John Wiley & Sons Ltd.",

year = "2022",

doi = "10.1111/bre.12748",

language = "English",

journal = "Basin Research",

issn = "0950-091X",

publisher = "John Wiley and Sons Inc.",

}

Pisani, L, Koltai, G, Dublyansky, Y, Kleine, BI, Whitehouse, MJ, Skrzypek, E, Carbone, C, Spötl, C, Antonellini, M, Bezerra, FH & De Waele, J 2022, 'Hydrothermal silicification and hypogene dissolution of an exhumed Neoproterozoic carbonate sequence in Brazil: Insights from fluid inclusion microthermometry and silicon-oxygen isotopes', Basin Research. https://doi.org/10.1111/bre.12748

TY - JOUR

T1 - Hydrothermal silicification and hypogene dissolution of an exhumed Neoproterozoic carbonate sequence in Brazil

T2 - Insights from fluid inclusion microthermometry and silicon-oxygen isotopes

AU - Pisani, Luca

AU - Koltai, Gabriella

AU - Dublyansky, Yuri

AU - Kleine, Barbara I.

AU - Whitehouse, Martin J.

AU - Skrzypek, Etienne

AU - Carbone, Cristina

AU - Spötl, Christoph

AU - Antonellini, Marco

AU - Bezerra, Francisco H.

AU - De Waele, Jo

N1 - Funding Information: This research was carried out in association with the ongoing R&D project registered as ANP 20502‐1, ‘—)—Porokarst—Processes and Properties in Fractured and Karstified Carbonate Reservoirs, sponsored by Shell Brasil under the ANP R&D levy as ‘’. Cave map data were kindly provided by (GPME). Cave sampling was performed through SISBIO permit 63178/1. We sincerely thank the Iramaia municipality (State of Bahia) and the Brazilian Federal Environmental Agency () for providing access to the cave and the special permission for collecting rock samples. We thank Bastian Joachim‐Mrosko for providing the access to the Raman Spectroscopy Laboratory at the University of Innsbruck and for his valuable help. We also thank Jürgen Konzett for the early discussions on monazite dating and Augusto Auler for the help during fieldwork. We finally thank the Editor Atle Rotevatn for handling the manuscript and the reviewers Marjan Temovski, Cathy Hollis and Alexander Klimchouk for their suggestions and comments that helped to improve our paper. This article is the NordSIMS published contribution n. 726. Processos e Propriedades em Reservartorios Carbonaticos Fraturados e Carstificados POROCARSTE 3D’ (UFRN/UNB/UFRJ/UFC/Shell Brasil/ANP Compromisso de Investimento com Pesquisa e Desenvolvimento Grupo Pierre Marin de Espeleologia Instituto Chico Mendes Publisher Copyright: © 2022 International Association of Sedimentologists and European Association of Geoscientists and Engineers and John Wiley & Sons Ltd.

PY - 2022

Y1 - 2022

N2 - Hypogene dissolution-precipitation processes strongly affect the petrophysical properties of carbonate rocks and fluid migration pathways in sedimentary basins. In many deep carbonate reservoirs, hypogene cavernous voids are often associated with silicified horizons. The diagenesis of silica in carbonate sequences is still a poorly-investigated research topic. Studies exploring the complexity of silica dissolution-precipitation patterns in hypogene cave analogues are therefore fundamental to unravel the diagenetic and speleogenetic processes that may affect this kind of reservoir. In this work, we investigated an exhumed and silicified Neoproterozoic carbonate sequence in Brazil hosting a 1.4 km-long cave. Quartz mineralization and silicified textures were analyzed with a multidisciplinary approach combining petrography, fluid inclusion microthermometry, silicon-oxygen stable isotope analyses and U-Th-Pb dating of monazite crystals. We found that an early silicification event caused the replacement of the dolostone layers with micro-crystalline quartz forming chert nodules. This event was likely associated with mixing fluids (ancient Neoproterozoic seawater and hydrothermal solutions sourced from the underlying Mesoproterozoic basement) at relatively low temperatures (ca. 50–100°C) and shallow depth. After the tectonic deformation produced by the Brasiliano orogeny, silica dissolution was promoted by high temperature and alkaline hydrothermal solutions rising from the quartzite basement along deep-rooted structures. Hypogene hydrothermal alteration promoted the dissolution of the cherty layers and the precipitation of chalcedony and megaquartz. Homogenization temperatures from primary fluid inclusions in megaquartz cement indicate minimum formation temperatures of 165–210°C. Similar temperature estimates (110–200°C) were obtained from the δ30Si and δ18O isotope systematics of quartz precipitated from hydrothermal solutions. The dissolved salts in the fluid inclusions were evaluated as NaCl + CaCl2 from microthermometric data combined with cryogenic Raman spectroscopy, corresponding to salinity ranging between 17 and 25 wt.%. No reliable age constraints for hydrothermal silica dissolution-precipitation phases were obtained from monazite U-Th-Pb dating. However, our results, interpreted in the regional context of the São Francisco Craton, suggest that the Cambrian tectono-thermal events could have been amongst the possible drivers for this hypogene process in the basin.

AB - Hypogene dissolution-precipitation processes strongly affect the petrophysical properties of carbonate rocks and fluid migration pathways in sedimentary basins. In many deep carbonate reservoirs, hypogene cavernous voids are often associated with silicified horizons. The diagenesis of silica in carbonate sequences is still a poorly-investigated research topic. Studies exploring the complexity of silica dissolution-precipitation patterns in hypogene cave analogues are therefore fundamental to unravel the diagenetic and speleogenetic processes that may affect this kind of reservoir. In this work, we investigated an exhumed and silicified Neoproterozoic carbonate sequence in Brazil hosting a 1.4 km-long cave. Quartz mineralization and silicified textures were analyzed with a multidisciplinary approach combining petrography, fluid inclusion microthermometry, silicon-oxygen stable isotope analyses and U-Th-Pb dating of monazite crystals. We found that an early silicification event caused the replacement of the dolostone layers with micro-crystalline quartz forming chert nodules. This event was likely associated with mixing fluids (ancient Neoproterozoic seawater and hydrothermal solutions sourced from the underlying Mesoproterozoic basement) at relatively low temperatures (ca. 50–100°C) and shallow depth. After the tectonic deformation produced by the Brasiliano orogeny, silica dissolution was promoted by high temperature and alkaline hydrothermal solutions rising from the quartzite basement along deep-rooted structures. Hypogene hydrothermal alteration promoted the dissolution of the cherty layers and the precipitation of chalcedony and megaquartz. Homogenization temperatures from primary fluid inclusions in megaquartz cement indicate minimum formation temperatures of 165–210°C. Similar temperature estimates (110–200°C) were obtained from the δ30Si and δ18O isotope systematics of quartz precipitated from hydrothermal solutions. The dissolved salts in the fluid inclusions were evaluated as NaCl + CaCl2 from microthermometric data combined with cryogenic Raman spectroscopy, corresponding to salinity ranging between 17 and 25 wt.%. No reliable age constraints for hydrothermal silica dissolution-precipitation phases were obtained from monazite U-Th-Pb dating. However, our results, interpreted in the regional context of the São Francisco Craton, suggest that the Cambrian tectono-thermal events could have been amongst the possible drivers for this hypogene process in the basin.

KW - fluid flow

KW - hydrothermal karst

KW - silica dissolution

KW - silicified reservoirs

UR - http://www.scopus.com/inward/record.url?scp=85146243710&partnerID=8YFLogxK

U2 - 10.1111/bre.12748

DO - 10.1111/bre.12748

M3 - Article

AN - SCOPUS:85146243710

SN - 0950-091X

JO - Basin Research

JF - Basin Research

ER -

Hydrothermal silicification and hypogene dissolution of an exhumed Neoproterozoic carbonate sequence in Brazil: Insights from fluid inclusion microthermometry and silicon-oxygen isotopes

Abstract

Bibliographical note

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